It is known that soil needs to be periodically aerated or de-compacted to encourage growth of a crop by facilitating the access of air, moisture, and nutrients to its roots and by providing space for the roots to grow. With relatively large areas, it is usual to effect aeration by means of tractor-towed aerating equipment. The purposes for which a given area is maintained can vary, requiring different kinds of aeration. It may be necessary to regularly aerate sub-soil without significantly disturbing the surface or, alternatively, it may be necessary to aerate an area while also turning over the surface soil. Also, aeration may be necessary with highly compacted soil, for example, in pasture land compacted by grazing animals; in such cases it is also usually necessary not to significantly disturb the surface.
Different types of aerating equipment have been employed in the past to effect aeration in different kinds of situations as mentioned above. For example, U.S. Pat. No. 4,383,580 to Huxford describes an aerating implement which is especially useful for aerating soil in pastures where it is necessary not to unduly disturb the surface. To achieve this, the aerating implement has a plurality of shafts rotatably mounted on a frame with their axes at an angle in the range of 70°–90° to the direction of travel, a plurality of substantially planar ground cutting and penetrating members mounted on the shaft with the plane of each cutting member at an angle of 70–90 degrees to the axis of its shaft towards its outer end. Since issuance of the Huxford patent, operation of the particular implement has been altered by re-orienting the cutting members such that the longitudinal centre line of each cutting member does not pass through the axis of rotation of the shaft (as taught in the Huxford patent), but is rather shifted rearwardly relative to the direction of movement of the shaft so that the longitudinal centre line of each cutting member is rearwardly spaced from the axis of rotation of the shaft, and also by twisting each cutting member by a small angle about its longitudinal centre line.
However, as suggested above, such an implement is not suitable for situations where it is desired to aerate the sub-soil and also turn over the surface. Another type of aerating implement thus has to be used in such situations, requiring the availability of two different types of aerating implement, which may be cost-prohibitive given the particular operator.
Prior attempts to address this problem have sought to provide aerating implements which are adjustable to enable both aeration without substantially disturbing the surface and aeration with turnover of the surface.
For example, U.S. Pat. No. 4,840,232 to Mayer discloses soil-aerating equipment which comprises a frame moveable in an intended direction of travel, at least a pair of gangs freely rotatably mounted on the frame for rotation about the longitudinal axis, such gangs extending in rearwardly-inclined opposite directions on opposite sides of a centre line of said frame extending in the direction of travel, means for adjusting the rearward inclination of the gangs to desired angles in the range of from about 90–120 degrees to the direction of travel, each gang carrying a series of soil-engaging substantially planar tines extending therefrom in vertical planes and positioned to sequentially engage and penetrate the soil with consequent rotation of the gangs when the frame is moved in the direction of travel, each tine having a central longitudinal axis which extends behind the gang's rotational axis at a distance therefrom in the range from about 0.25 to about 1.75 inches, and each tine being twisted about the tine central longitudinal axis at an angle to a vertical plane parallel to the direction of travel in the range of from about 1–30 degrees.
It has been found that soil aeration without significantly disturbing the surface can be effected by positioning the gangs at an angle to the direction of travel in the lower part of the angular range taught by the Mayer patent, and that soil aeration with surface turnover can be effected by positioning the gangs at an angle to the direction of travel in the upper part of the specified angular range. An operator can thus utilize the same piece of equipment for both purposes, thereby saving not only the cost of having to provide another item of equipment but also saving time because aeration equipment in accordance with the invention can readily be adjusted for use in one situation or the other. Thus, an operator does not have to return from a work area to another place to change equipment.
However, with some aeration equipment comprising at least a pair of gangs each journalled for rotation at their respective ends and supported by bearings at the respective ends where the gangs are typically positioned along a common axis in side-by-side arrangement, a problem arises in that a gap is effected between tine assemblies on adjacent gangs, due to space required to journal the respective ends and provide securement of the aeration device to the equipment frame. Such a gap is often greater than the individual spacing between tines on the gangs, particularly where the tines on each gang are spaced relatively close to each other. The undesirable result is a wide strip of soil intermediate the pair of gangs where no aeration is effected.
In order to overcome this problem, the Mayer device incorporated a cantilevered tine assembly at each gang end, outboard of the bearings on which the gangs were journalled. The tines were therefore able to be positioned intermediate the journalled ends of the gangs and thus could aerate the soil in the area intermediate adjacent gangs.
However, the cantilevered tine assembly of Mayer was of integral construction, which proved disadvantageous in some situations. Should one of the tines in the integral tine assembly become damaged or irreparably worn, replacement of the whole integral assembly was necessary. This proved to be both expensive and time-consuming, as tines would frequently become broken, particular in rocky areas.